Fuels used in refineries and petrochemical plants frequently contain sufficient sulfur to present corrosion problems. Walls of direct fired heaters are subject to corrosion when such high sulfur fuels are being burned. The corrosion is a result of condensation of sulfur oxides on the metal casings and combination of these sulfur oxides with water vapor whereby sulfuric and sulfurous acids are produced. These acids attack the metal casings from inside the heaters thus resulting in severe damage.
One effective way to avoid sulfur corrosion in a direct fired heater is to operate the heater with its metal casing temperature above the dew points of the sulfur oxides, thereby avoiding condensation of the sulfur oxides. However, such operation results in high heat losses from the heater and such operation cannot be maintained under all ambient conditions. Other approaches have been tried to prevent sulfur corrosion, including special coatings and special refractory linings, but none of these approaches have proven to be fully satisfactory.